Temperature-increase warning device



25, 1969v A. G. HERON TEMPERATURE-INCREASE WARNING DEVICE Fi led Oct. 11 1966 .PIIPIIIIII Lrll l f INVENTOR; A/M /YK/ 60r7c 14 6/3 United States Patent US. Cl. 337-332 8 Claims ABSTRACT OF THE DISCLOSURE A switch designed to activate an alarm or warning device includes two contact members, one of whlch is movable into one of two positions, which are located in a fluid having a freezing point within a desired range.

The movable contact is, either mechanically or magnetically biased by a switch operating means into .one of the two positions which may either make or break the alarrn actuating. circuit. The switch operating means may be in the form ofa weight or a weighted magnet which moves the movable contact into a position relative to the second contact which serves either to make or break the circuit thereby activating the alarm system. The weight or weighted .magnet is maintained in its initial position due to the liquid surrounding the contacts being in a frozen or solidified state. Upon melting, the contacts are allowedto move into the second of twopositions due to the biasing influence of the weight or weighted magnet.

This invention relates to temperature-increase"alarm devices. I 1 I The invention is primarily concerned with cold storage systems, such as for example, deep freeze cabinets, refrigerators, and cold rooms which are always subject to the danger of temperature rise because of failure of the refrigeration plant or for any other cause. However, the'device of the-present invention is not confined to use in such systems since it may be made equally responsive to temperature increases at higher temperatures and may even be used as fire warning device.

An object of the invention is to provide a cheap and effective alarm operative when a temperature rises above a predetermined level.

According to the invention a temperature-increase alarm device comprises a housing prov ided with a compartment for accommodating a liquid having a predetermined freezing or solidifying point, and switch operating means for causing or allowing the contacts of a switch to be open (or closed) whilethe liquid is frozen or solidified and allowing the contacts to close (or open) when the frozen or solidified liquid melts, whereby an alarm system may be operated to give warning of an undesired temperature increase.

Usually a weight is employed for being releasably frozen and operating the switch, for example in conjunction with one of the contacts or for operation of an independently mounted switch. The weight may be in the form of a magnet for operating a magnetic switch.

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The invention will now be particularly described, by way of example, with reference to the' accompanying drawings, in which:

FIG. 1 is a perspective view, partly broken away of a weight-operated temperature alarm device for a deep freeze;

FIG. 2 shows the device of FIG. 1 in a different position;

FIGS. 3 and 4 show alternative embodiments including magnets for operation of the contacts of a switch;

FIG. 5 is a perspective view partly broken away, of a further embodiment having a magnetically operated switch; and

FIG. 6 shows a preferred alternative of the embodiment of FIG. 5.

Referring to FIGS. 1 and 2, a temperature-increase alarm device, such as may be used in a cold storage systern, includes two contact arms 10 and 11 mounted in a closed housing 12. The contact arms project outside the housing to provide terminals 13 and 14. The contact arm 11 is arranged to be flexible and carries a contact 16 co-operating with the contact 15 and, on the other side of the arm 11, a Weight 17. The housing 12 contains a quantity of liquid 18 having a freezing-point at a temperature 10 to 15 F. higher than the temperature of the deep, freeze.,The housing 12 has an abutment 19 en abling the housing to be placed in an inclined position.

In operation the terminals 13 and 14 are coupled to a bell and battery (not shown), or through a relay for mains operation. The housing is then partly filled with the liquid, sealed, and then laid on its side in the deep freeze so that the flexible arm 11, assisted by the weight 17, moves apart from the arm 10 and opens the contacts 15 and 16. The liquid 18 freezes and the housing 12 is then stood upright, in which position the contacts 15 and 16 will be maintained open by the frozen liquid.

In the event of the temperature of the deep freeze rising above the melting point of the liquid 18 due to a power failure or any other reason, the melting of the liquid 18 allows the contacts 15 and 16 to close and the alarm is operated. Immediate attention can then be given to the fault and the housing placed on its side to be refrozen when conditions return to normal.

Alternatively the contacts may be closed and the liquid frozen so as to hold the contacts together. Any undue temperature rise would then cause the contacts to break any alarm circuit in which they were included.

The temperature of the deep freeze may be -5 F., in which case'a liquid freezing-point in the range from +5 to +10 F. would allow ample time for the repair to be carried out without damage to the food stored.

In domestic refrigerators or certain cold rooms the liquid could be water, depending upon the temperature of the refrigerating chamber, or glycol could be used if lower temperatures are required.

FIG. 3 shows a magnet-operated alternative embodiment of the invention comprising a housing 21 which is preferably of generally H-section, the flanges being of the order of to thick whilst the web is formed as a container for the liquid, magnet and switch. Any suitable heat conducting plastics material capable of withstanding cold can be used, provided it is not subject to degenera- 3 tion by the enclosed liquid. The liquid is so chosen that it solidifies at the highest permissible temperature of the cold storage system.

The switch itself is one which is operated by a magnetic field and has a normally open contact. It is so located in the housing that movement of the magnet through the liquid to a position adjacent the switch, closes the contacts and operates the alarm.

The housing 21 has thin walls, and includes a chamber 22 adapted to contain a liquid which solidifies at the desired temperature. A magnet 23 is placed in the liquid and the chamber closed by an end lid. A switch 24, disposed in the housing; has two leads 25a and 25b connected through the housing; this switch 24 normally has its contacts open when the magnet 23 is positioned remote therefrom.

The device is operated as follows:

The housing 21 is turned to a position in which the magnet 23, due to its own weight, falls through the liquid so as to assume a position remote from the switch 24; the device is then placed in the refrigerator. After the liquid has solidified, due to freezing, the entire housing is turned through 180 so that the magnet 23 is vertically above the switch but held remote therefrom due to being frozen in position. A small amount of water is applied to the hOUSing on the outside of a flange so that when the switch is stood in position in the cold chamber it will remain where placed. If the temperature in the cold store rises excessively, the magnet drops through the unfrozen liquid and thus open the contacts of the switch to actuate the alarm.

The device shown in FIG. 4 is similar to that shown in FIG. 3 except that a second magnet 26 of the same polarity as the magnet 23 is permanently fixed adjacent the switch 24.

The operation of the device shown in FIG. 4 is as follows:

The magnet 26 biases the contacts of the switch 24, but does not quite close them, if the magnet 23 is remote therefrom. The housing 21 is turned into a position in which the magnet 23 falls therethrough due to its own weight, and the combined fields of the magnets then act on the contacts to close them.

The magnets may alternatively be arranged such that the second magnet of the same polarity as the first-mentioned magnet is provided permanently associated with the magnetic switch for preventing the first magnet from actuating the switch contacts when it held its frozen or solidified position remote from the switch and so that the first magnet, on moving towards the switch overcomes the force of the second magnet and actuates the switch and thereby the alarm system.

The main advantage of the embodiments shown in FIGS. 3 and 4 is that the contacts do not lie in the solidifiable liquid and are therefore not liable to wetting or corrosion. The contacts themselves may be sealed in a glass tube filled with an inert gas or evacuated, so as to offer still further protection against corrosion.

The preferred device shown in FIG. comprises a U- shaped support which may be formed from aluminum sheet with standing arms 30, 31 and a tubular container 32 also of non-ferrous material, for guiding a magnet weight 33, welded, adhered or otherwise secured between the arms 30, 31 through one of which a non-ferrous bolt plug 36 is provided for allowing the insertion of liquid 18 into the container. A magnetically operated switch 24 is mounted near one end of the container for operation by the magnet 33 when the latter is at the adjacent end of the container.

Conveniently the magnetic switch is carried in an aperture in a conductor connector 34 secured to the standing arm 31 and leads 25a and 25b extend to a battery and bell (not shown).

In operation sufficient liquid is inserted in the tube 32 to cover a substantial part of the magnet 33 and the bolt 36 is replaced; the device is then stood in a deep freeze compartment of a refrigerator on the arm 30",projection of the bolt 36 minimizing sticking of the arm 30 to the supporting surface, and the liquid freezes around the magnet, anchoring it in the position shown. The device is then stood on the arm 31 in the place, such as a cold room, where it is to be used and connected in the alarm circuit. Upon the temperature rising above the freezing point of the liquid 18, this melts, releasing the magnet 33 to allow it to fall into proximity with switch 24 which is consequently operated to sound the alarm.

FIG. 6 shows a modification of the embodiment shown in FIG. 5, and in which the switch 24 is housed in a tubular container 37 disposed substantially parallel with the liquid container 32. Like the container 32, container 37 is secured between the arms 30 and 31. Access for leads 25a, 25b is through an opening in plate 30, the container 37 subsequently being stopped by resin, adhesive or other suitable substance.

It will be readily understood that the invention is not limited to use in cold storage systems, since it is only necessary to use substances with a higher solidification or melting point, such as e.g., paraflin Wax or benzine, for the device to be operated at any desired temperature. The invention is, therefore, to be limited only by the scope of the appended claims.

I claim:

1. A temperature increase alarm device comprising a housing including a compartment for accommodating a fluid having a predetermined freezing or solidifying point, a switch mounted in the housing, the switch comprising a movable first contact and a second contact, a switch operating means movably mounted within the fluid compartment and in direct contact with said fluid, the switch operating means comprising a weight having a specific gravity different from'that of said fluid, said switch operating means being located in a first position in said fluid compartment when said fluid is in its frozen or solidified state and being movable to a second position in said fluid compartment when the frozen or solidified fluid melts, said switch operating means cooperating with the movable contact to maintain it in a first position while the fluid is frozen or solidified and moving the movable contact to a second position when the frozen or solidified fluid melts, the second contact mounted on the housing in close proximity to the movable contact, whereby said switch is operated by movement of said weighted switch operating means through said fluid to said second position, due to the difference between the specific gr'avities of said switch operating means and said fluid, upon the fluid changing from a solid to a liquid state, so as to activate an alarm system to give warning of an undesired temperature increase.

2. A device according to claim 1 wherein the switch 1 operating means is a weight movably supported in said. compartment, said weight having a higher specific gravity. than said fluid, whereby the weight biases the movable contact from one of said positions to the other upon a change in the fluid from a solid to a liquid state.

3. A device according to claim 2, wherein said movable contact is mounted within the fluid compartment and the weight is attached directly to the movable contact.

4. A device according to claim 1 wherein the switch is magnetically operable and mounted outside the fluid compartment, said switch operating means is a magnet movably mounted within said fluid compartment, said magnet being located in a first position remote from said switch when the fluid is in a frozen or solidified state and being movable through said fluid to a second position adjacent the switch upon a change in the fluid from a solid to a liquid state, whereby the movable contact is in a first position while the magnet is remote from the switch and is moved to a second position by magnetic force when the magnet is adjacent the switch.

5. A device according to claim 4 further comprising a second magnet of the same polarity as the first mentioned magnet, said second magnet fixedly mounted on said housing directly adjacent the magnetically operable switch so as to bias the movable contact towards its first position to prevent the switch from being inadvertently operated by said first magnet while located in its first position remote from the switch.

6. A device according to claim 4, wherein said magnetically operable switch is housed in an individual compartment mounted on said housing directly adjacent to and separate from the fluid compartment.

7. A device according to claim 1, wherein said solidiliable fluid comprises a substance selected from the group consisting of water, glycol, parafi'in Wax and benzine.

8. A device according to claim 1, wherein said housing is made from a plastics material.

6 References Cited UNITED STATES PATENTS BERNARD A. GILHEANY, Primary Examiner H. B. GILSON, Assistant Examiner US. Cl. X.R. 

